WO2012120620A1

WO2012120620A1 - Battery state estimating method and battery management system

Info

Publication number: WO2012120620A1
Application number: PCT/JP2011/055251
Authority: WO
Inventors: 井上　健士; 二見　基生; 洋平河原; 本田　光利
Original assignee: 株式会社日立製作所
Priority date: 2011-03-07
Filing date: 2011-03-07
Publication date: 2012-09-13
Also published as: US20130320989A1; EP2685269A4; EP2685269A1; KR20130121143A; CN103392133A; JPWO2012120620A1

Abstract

In this battery state estimating method, a current value and a terminal voltage value of a battery (B) are measured by means of a current detection unit (10) and a voltage detection unit (12) when a current is being charged or discharged, and on the basis of the current value and the terminal voltage value thus measured, at least one of charging rate, deterioration level or full charge quantity is calculated as a battery state. In the cases where a change of the measured current value per one second is a predetermined value or more, a current and a terminal voltage measured in a predetermined period of time after generation of the current change are not used, and on the basis of a current value and a terminal voltage value, which are measured during the charge/discharge period other than such period of time, at least one of the charging rate, the deterioration level or the full charge quantity of the battery (B) is calculated.

Description

Battery state estimation method and battery management system

The present invention relates to a battery state estimation method for detecting a battery state and a battery management system.

Conventionally, as a method for estimating the full charge capacity and the degree of deterioration (SOH; State of Health) of a battery, the battery voltage is measured when the battery current is not flowing at the time of system suspension, and the voltage and the charge rate (SOC; Measure the charge rate with reference to the map that shows the relationship between (Charge) and use the charge (integrated current during operation) used between pauses and pauses. There is a method in which the full charge capacity is measured and the SOH is set to (full charge capacity) / (initial full charge capacity) (see Patent Document 1). In addition, as a definition of system suspension, the battery stopped charging / discharging, and it was set as 1 minute or more.

Japanese Unexamined Patent Publication No. 6-242193

Although the conventional method described above can be applied when the system is frequently stopped in an automobile, it is difficult to apply to a system such as a power system where the system is stopped only during maintenance.

According to the first aspect of the present invention, the battery state estimation method measures the current value and the terminal voltage value of the battery at the time of charging and discharging the battery, and based on the measured current value and the terminal voltage value, A battery state estimation method for calculating at least one of a charging rate, a degree of deterioration, and a full charge capacity, and when a change in measured current value per second is a predetermined value or more, occurrence of a current change The battery charging rate based on the current value and the terminal voltage value measured in the battery charging / discharging period other than the above period is not used. And calculating at least one of the deterioration degree and the full charge capacity.
According to the second aspect of the present invention, the battery management system includes a current detection unit that detects a current value of the battery, a voltage detection unit that detects a terminal voltage value of the battery, and a current value detected by the current detection unit. A current change detection unit that detects a current change whose change per second is equal to or greater than a predetermined value, and a current value and a terminal voltage detected in a period from when the current change is detected by the current change detection unit until a predetermined time elapses. Battery state calculation that calculates at least one of the charging rate, the degree of deterioration, and the full charge capacity as the battery state based on the current value and the terminal voltage value detected in the battery charging / discharging period other than the period without using the value A section.
According to the third aspect of the present invention, in the battery management system of the second aspect, it is preferable to use the smallest polarization time constant of the battery polarization time constant or 2 seconds for a predetermined time.
According to the fourth aspect of the present invention, in the battery management system of the second or third aspect, it is preferable to use a current value corresponding to a discharge rate of 0.1 C as the change in the current value per second.
According to a fifth aspect of the present invention, the battery management system according to any one of the second to fourth aspects includes a display device that displays the battery state calculated by the battery state calculation unit.
According to the sixth aspect of the present invention, in the battery management system according to any one of the second to fourth aspects, the charging is performed within a predetermined number from the present time to the past among the charge rates calculated by the battery state calculation unit. The battery state calculation unit calculates the full charge capacity when the difference between the maximum value and the minimum value of the charge rate stored in the storage unit is equal to or greater than the predetermined charge rate difference. It is intended to be.
According to a seventh aspect of the present invention, in the battery management system of the sixth aspect, the predetermined charging rate difference is 15%.
According to an eighth aspect of the present invention, in the battery management system according to the sixth or seventh aspect, the battery management system includes a display device that displays the battery state calculated by the battery state calculation unit, and the display device is charged by the battery state calculation unit. When the rate is calculated, the display of the charge rate is updated with the calculated charge rate, and when the full charge capacity corresponding to the charge rate has not been calculated, the most recently calculated full charge capacity and the The battery deterioration level based on the full charge capacity is displayed.
According to the ninth aspect of the present invention, in the battery management system of the eighth aspect, when displaying the most recently calculated full charge capacity and the degree of deterioration of the battery based on the full charge capacity, the full charge capacity and It is preferable to make the display form of the deterioration degree different from the display form in the case of displaying the full charge capacity corresponding to the charging rate.
According to a tenth aspect of the present invention, in the battery management system according to the second aspect, the battery is composed of a plurality of battery cells, and the battery state detection unit is at least one of a battery charge rate, a degree of deterioration, and a full charge capacity. Is calculated for each of the plurality of battery cells.
According to an eleventh aspect of the present invention, in the battery management system according to the second aspect, the battery includes a plurality of battery blocks each including a plurality of battery cells, and the battery state detection unit includes the battery charge rate, the degree of deterioration, and the fullness. At least one of the charging capacities is calculated for each of the plurality of battery blocks.
According to a twelfth aspect of the present invention, in the battery management system according to the tenth or eleventh aspect, the connection of the plurality of batteries includes at least a series connection, and the detection of the current value and the terminal voltage value is performed in series. A synchronization device that synchronizes the detection by the current detection unit and the detection of each battery by the voltage detection unit is provided so as to be performed at the same time between the batteries.
According to a thirteenth aspect of the present invention, the battery management system according to the eleventh aspect includes a display device that displays the battery state calculated by the battery state calculation unit, and the display device is calculated by the battery state calculation unit. A battery state is displayed for each of the plurality of battery blocks.

The present invention can estimate the battery state such as the capacity and the degree of deterioration with higher accuracy during charging / discharging even when there is no clear battery halt condition.

It is a functional block diagram which shows the structure of the battery management system which concerns on this embodiment. It is a flowchart explaining the process in a battery management system. It is a figure which shows typically the relationship between the change of an electric current value, and the error of the calculated charging rate. It is a figure which shows an example of the circuit model of a battery. It is a flowchart which shows an example of the detailed process of step S22. It is a figure explaining charge rate calculation condition judgment processing. 2 shows an example of an open-circuit voltage-charge rate (SOC) map. It is a figure which shows the graph of open circuit voltage-SOC. FIG. 4 is a diagram showing a table in the SOC / charge storage unit 14. It is a figure explaining how to obtain the full charge capacity. FIG. 10 is a diagram showing a display example of the display unit 19. It is a figure which shows a system configuration | structure, when a total of four 2 series batteries of 2 parallel are connected. It is a figure which shows the example of a display in the display part 913 at the time of connecting a battery in series. It is a block diagram which shows the drive system of the rotary electric machine for vehicles to which the battery management system by this Embodiment is applied.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram showing the configuration of the battery management system according to the present embodiment. The battery management system according to the present embodiment is applied to devices such as an electric vehicle and a power system, and estimates the full charge capacity of the battery while these devices are in operation. The battery management system includes an ammeter 10, a current integration unit 11, a voltage detection unit 12, a voltage correction unit 13, an SOC / charge storage unit 14, a measurement timing designation unit 15, an SOC estimation map 16, an update command unit 17, a full charge capacity. It comprises a calculation unit 18 and a display unit 19.

In the configuration shown in FIG. 1, the current integration unit 11, the voltage correction unit 13, the SOC / charge storage unit 14, the measurement timing designation unit 15, the SOC estimation map 16, the update command unit 17, and the full charge capacity calculation unit 18 are
It is realized by a controller provided on the device system side, for example, a notebook PC, a controller in an electric vehicle, or software in a power system controller. For example, in the case of an electric vehicle, it is realized by software of a battery controller provided for battery control. Of course, a controller dedicated to the battery management system may be provided and executed.

The software in the controller is realized by a state detection device (battery temperature, current, voltage measurement device) directly connected to the battery, a controller of the moving body, a controller of the generator, or a combination of various controllers. You may do it. The display unit 19 is realized by a display device and a display provided separately. Here, the display device may be placed in the vicinity of the battery, or information on the charging rate and the full charge capacity may be sent to a remote place via a communication line, and the display device may be prepared and displayed at the remote place.

The ammeter 10 measures the current charged and discharged in the battery. The ammeter uses a shunt resistor or a Hall element (reference patent, Japanese Patent Laid-Open No. 10-62453). The voltage detection unit 12 in FIG. 1 measures the voltage (analog value) between the negative electrode and positive electrode of the battery B, converts it to a digital value, and sends voltage information to the voltage correction unit 13. The battery B in FIG. 1 is a secondary battery such as a lead battery or a lithium ion battery, or an electric double layer capacitor or a lithium ion capacitor.

FIG. 14 is a block diagram showing an example of a drive system of a vehicular rotating electrical machine to which the battery management system according to the present embodiment is applied. The drive system shown in FIG. 14 includes a battery module 9, a battery monitoring device 100 that monitors the battery module 9, an inverter device 220 that converts DC power from the battery module 9 into three-phase AC power, and a motor 230 for driving the vehicle. ing. The battery management system of this embodiment is adopted for the battery monitoring device 100.

The motor 230 is driven by the three-phase AC power from the inverter device 220. The inverter device 220 and the battery monitoring device 100 are connected by CAN communication, and the inverter device 220 functions as a host controller for the battery monitoring device 100. Further, the inverter device 220 operates based on command information from a host controller (not shown).

The inverter device 220 includes a power module 226, an MCU 222, and a driver circuit 224 for driving the power module 226. The power module 226 converts the DC power supplied from the battery module 9 into three-phase AC power for driving the motor 230. Inverter device 220 controls the phase of AC power generated by power module 226 with respect to the rotor of motor 230, and causes motor 230 to operate as a generator during vehicle braking. The three-phase AC power generated by the motor 230 is converted into DC power by the power module 226 and supplied to the battery module 9. As a result, the battery module 9 is charged.

The battery module 9 is composed of two battery blocks 9A and 9B connected in series. Each battery block 9A, 9B is provided with 16 battery cells connected in series. The battery block 9A and the battery block 9B are connected in series via a maintenance / inspection service disconnect SD in which a switch and a fuse are connected in series. By opening this service disconnect SD, the direct circuit of the electric circuit is cut off, and even if a connection circuit is formed at one place between the battery blocks 9A and 9B and the vehicle, no current flows. With such a configuration, high safety can be maintained.

A battery disconnect unit BDU including a relay RL, a resistor RP, and a precharge relay RLP is provided in the high-voltage line HV + between the battery module 9 and the inverter device 220. A series circuit of the resistor RP and the precharge relay RLP is connected in parallel with the relay RL.

The battery monitoring device 100 mainly performs measurement of each cell voltage, measurement of total voltage, measurement of current, cell temperature, cell capacity adjustment, and the like. For this purpose, IC1 to IC6 as cell controllers are provided. The 16 battery cells provided in each battery block 9A, 9B are each divided into three cell groups, and one IC is provided for each cell group.

IC1 to IC6 communicate with the microcomputer 30 in a daisy chain manner via an insulating element (for example, a photocoupler) PH, a communication system 602 for reading a cell voltage value and transmitting various commands, and only cell overcharge detection information. And a communication system 604 for transmitting. In the example shown in FIG. 14, the communication system 602 is divided into an upper communication path for IC1 to IC3 of the battery block 9A and a lower communication path for IC4 to IC6 of the battery block 9B. A current sensor Si such as a Hall element is installed in the battery disconnect unit BDU, and the output of the current sensor Si is input to the microcomputer 30. Signals related to the total voltage and temperature of the battery module 9 are also input to the microcomputer 30 and measured by an AD converter (ADC) of the microcomputer 30. Temperature sensors are provided at a plurality of locations in the battery blocks 9A and 9B.

FIG. 2 is a flowchart for explaining processing in the battery management system shown in FIG. The processing of the flowchart shown in FIG. 2 is executed when a device (electric vehicle, notebook PC, power system, etc.) provided with a battery management system starts to operate, at regular time intervals or at predetermined conditions until the device stops. Every time it is established, it is repeated periodically. When the program is executed at regular time intervals, for example, the execution cycle is set to a predetermined value (for example, 100 ms).

(Step S20)
In step S20, the charge / discharge current value of the battery B is measured by the ammeter 10 of FIG.

(Step S21)
In step S21, a charge (current integration) is calculated based on the current value measured in step S20. That is, the charge (Ah) is calculated by (current value) × (time), and the time here is an elapsed time from the previous current measurement to the current current measurement, and the execution cycle described above is used. Note that the initial charge value at the start of operation (charge / discharge start) is set to zero. The charge calculation process in step S21 corresponds to the current integration unit 11 in FIG.

(Step S22)
In step S22, it is determined whether or not the charging rate calculation condition is met based on the current change rate, that is, whether or not the charging rate is calculated at the current measurement timing (program processing timing in FIG. 2). FIG. 3 is a diagram illustrating determination of the charging rate calculation condition in step S22, and FIG. 5 is a flowchart illustrating an example of detailed processing in step S22. In addition, the process of step S22 corresponds to the process of the measurement timing designation | designated part 15 of FIG.

In the present embodiment, the battery state (charge rate (SOC: State of Charge), degree of deterioration, full charge capacity) is calculated based on the current value and the terminal voltage measured during operation (charging / discharging). I have to. During operation, the current value changes according to the state of the load (for example, a motor). Then, as shown in FIG. 3, if the battery state is calculated using the current value and the voltage value measured immediately after the current value suddenly changes, the calculation error increases.

FIG. 3 is a diagram schematically showing a relationship between a change in current value and an error in the calculated charging rate. A case where the current value changes by ΔI at time ta is shown. When the current value changes in this way, the calculated charging rate error changes greatly immediately after the current value changes, and thereafter, the error decreases after a certain amount of time has elapsed. Generally, if the elapsed time after the current value changes is 2 seconds or more, the error is sufficiently small. In the present embodiment, it is considered that the current value and the voltage value measured until a predetermined elapsed time elapses from the change of the current value are not used for calculation of the battery state (charging rate, deterioration degree, full charge capacity). Thus, the calculation accuracy of the battery state is improved. Hereinafter, the predetermined elapsed time τ is referred to as a waiting time τ.

Therefore, in the charging rate calculation condition determination process in step S22 of FIG. 2, whether or not a current change greater than or equal to a predetermined value has occurred at the current process timing, or during a waiting time when there is a current change greater than or equal to a predetermined value It is determined whether or not. If a current change occurs or during a waiting time, it is determined that the condition is not satisfied, and the program of FIG. 2 is terminated. On the other hand, if it is determined that it is not during the waiting time, the process proceeds from step S22 to step S23.

Here, the current change is a current change per second, and a determination value for determining the current change is, for example, a current change per second that is a constant multiple C (the initial full charge capacity of the battery B). C: discharge rate). Generally, it is better to set to about 0.1C. In the case of a battery having an initial full charge capacity = 5 Ah, 0.1 C is 0.5 A, and therefore, a current change of 0.5 A or more occurs per second. 0.1C is an example, and it may be 0.3C larger than 0.1C. For example, an optimal value may be set by testing with an actual machine in advance.

Further, the waiting time τ may be a predetermined value (for example, 2 seconds described above), or may be the shortest time among the polarization time constants of the battery. The larger the waiting time τ is set, the smaller the error is. On the other hand, the number of measurement data to be used for battery state calculation is reduced, and it is difficult to obtain the calculation timing. Therefore, in order to achieve both calculation frequency and error reduction, it is preferable that τ be in the order of seconds both when a constant value is used and when the polarization time constant of the battery is used.

The polarization time constant will be described with reference to FIG. FIG. 4 is a diagram showing an example of a circuit model of a battery, which is an ideal battery 31 (voltage after several hours since charging / discharging of the battery is stopped), DC resistance 32, polarization 1 (33), polarization 2 (34), It consists of + pole 35. Here, polarization is expressed as a parallel connection of a resistor and a capacitor. The time constant of polarization 1 is τ1 = C1 · R1, the time constant of polarization 2 is τ2 = C2 · R2, and τ1 <τ2. Here, τ1 is a time constant of about several seconds depending on the battery, and τ2 is a time constant of several minutes to several hours. Here, τ1 is used as the waiting time τ described above. 4 may be measured using a known electrochemical impedance (EIS) measurement method (AC impedance method) (Masayuki Itagaki: electrochemical impedance method principle, measurement / analysis, Maruzen).

Further, instead of the time constant of polarization, τ calculated by the following equation (1) may be used as the above-described waiting time τ. The voltage per SOC 1% will be described in step S24 described later. The SOC error is a predetermined value (for example, 5%).
τ = τ1 × ΔI × R1 / v (1)
v = SOC 1% voltage × SOC error τ1: The shortest time among the polarization time constants ΔI: Current difference (measured current one cycle before this time)
R1: R1 in FIG.

Next, details of the charging rate calculation condition determination process in step S22 will be described with reference to FIG. In step S220, whether the current change per second obtained by dividing the difference ΔI between the current measured current value measured by the ammeter 10 and the previous measured current value by the execution period (100 ms described above) is a predetermined value or more. Determine whether or not. If it is determined in step S220 that the current change is equal to or greater than the predetermined value, the process proceeds to step S225, and the count number N is set to N = 1. The count number N is an index indicating the elapsed time since the current value has changed by a predetermined value or more, and the elapsed time is represented by N × execution cycle (for example, 100 ms). The count number N is stored in a memory provided in the controller, and the value of N at the start of operation is 0. When the process proceeds from step S220 to step S225, there is a current change of a predetermined value or more, so the charging rate calculation condition is not satisfied and the program of FIG. 2 is terminated.

On the other hand, if it is determined in step S220 that the current change is smaller than the predetermined value, the process proceeds to step S221 to determine whether the count number N is N ≠ 0. If N ≠ 0 is determined in step S221, the process proceeds to step S222. If N = 0 is determined, the process proceeds to step S23 in FIG.

In step S222, it is determined whether the count number N satisfies N = M. Here, M is an integer that satisfies the equation “M × execution cycle ≧ τ> (M−1) × execution cycle”. In step S222, it is determined whether or not the elapsed time is equal to or greater than the waiting time τ. Yes. If N ≠ M in step S222, that is, if it is determined that the elapsed time has not reached the waiting time τ, the process proceeds to step S224, and the count number N is increased to N = N + 1. When the process of step S224 is completed, the program of FIG. 2 is terminated.

On the other hand, if it is determined in step S222 that N = M, that is, if it is determined that the elapsed time is equal to or longer than the waiting time τ, the process proceeds to step S223 and the count is set to N = 0, and then to step S23 in FIG. move on.

The above-described charging rate calculation condition determination process in FIG. 5 will be described with reference to FIG. FIG. 6 is a diagram showing changes in current, and t0 to t10 indicate processing timings when the program shown in FIG. 2 is executed. The current value changes by ΔI1 between time t0 and time t1, changes by ΔI2 between time t5 and time t6, and changes by ΔI3 between time t6 and time t7. Here, any change amount ΔI1 to I3 is considered to be larger than the predetermined value when converted into a current change for one second. Further, M related to the waiting time τ is M = 3.

At the program processing timing at time t1, after YES is determined in step S220 in FIG. 5 and N = 1 is set in step S225, the processing after step S23 in FIG. 2 (including charge rate calculation and the like) is not executed. Exit the program. By setting N = 1 in step S225, the calculation of the elapsed time is started.

At the subsequent program processing timing at time t2, since the current change is zero, NO is determined in step S220, and the process proceeds to step S221. Since the count number N is set to N = 1 in the process at the previous time t1, YES is determined in step S221, and the process proceeds to step S222. In step S222, it is determined that N.noteq.M (NO), and in step S224, N = 1 + 1 = 2. Then, the program is terminated without executing the processes in and after step S23 in FIG. Also in the program processing cycle at time t3, since the current change is zero, the process proceeds in the same manner as in step S220 → step S221 → step S222 → step S224, and after N = 2 + 1 = 3 in step S224, the program ends. To do.

Even at the program processing timing at time t4, since the current change is zero, the process proceeds from step S220 to step S221 to step S222. However, since N = 3 (= M), YES is determined in step S222. As a result, the process proceeds from step S222 to step S223, the count number N is set to N = 0, and the process proceeds to step S23 in FIG. That is, at time t4, the elapsed time after the current change greater than or equal to the predetermined value is equal to or longer than the waiting time τ, and the battery state such as the charging rate is calculated based on the current value measured in step S20.

At the program processing timing at time t5, since the current change is zero and N = 0, the process proceeds in the order of step S220 → step S221 → step S222 → step S223. Therefore, also in the program processing timing at time t5, the processing after step S23 is executed, and the battery state such as the charging rate is calculated.

At the subsequent program processing timing at time t6, since the current change with respect to the current value at time t5 is equal to or greater than the predetermined value, the process proceeds from step S220 to step S225, the count number N is set to N = 1, and the program ends.

At the program processing timing at time t7, since the current value increases again and the current change becomes equal to or greater than the predetermined value, YES is determined in step S220, and the count number N is again set to N = 1 in step S225. That is, the elapsed time measurement start time is updated at time t7.

At the program processing timing at time t8, since the current change is zero, the process proceeds from step S220 to step S221. Since the count number N is N = 1 at time t8, the process proceeds from step S221 to step S222 to step S224. In step S224, the count number N is set to N = 1 + 1 = 2. Then, the program of FIG. 2 is terminated. The program processing timing at time t9 and time t10 is the same as that at time t4 described above. Therefore, when the elapsed time from the current change between time t6 and time t7 becomes equal to or longer than the waiting time τ, calculation of the battery state such as the charging rate is started again. By performing the process as shown in FIG. 5, when there is a current change of a predetermined value or more, the battery state is calculated after a predetermined waiting time has elapsed. Can be suppressed and the calculation accuracy can be improved.

(Description of step S23)
Next, the process of step S23 will be described. In addition, the process of step S23 corresponds to the process of the voltage correction part 13 in the functional block diagram of FIG. In step S23, the current and voltage are measured by the ammeter 10 and the voltage detection unit 11, and based on the measured current value and voltage value, the battery is left for several hours in a state where there is no charge / discharge of the battery. The battery terminal voltage is estimated using equation (2).
Open-circuit voltage = V + I · R-Vf (2)
In the formula (2), V, I, R, and Vf are as follows.
V: Measured battery voltage I: Measured current (positive for discharging and negative for charging)
R: DC resistance of the battery (resistance after the measurement cycle when the current changes)
Vf: battery polarization voltage

Here, V and I in the equation (2) are known because they are measured, but the DC resistance R and the polarization voltage Vf are unknown, and thus need to be estimated. As an estimation method of the DC resistance R, the formula (3) may be used, or a table (index is set to SOC (charge rate) or SOH (degradation degree: State of Health), temperature) is set in advance). You may make it refer to a value. When using a table, a thermometer for measuring the battery temperature is provided, and the measured temperature is used when referring to the table.
R = ΔV / ΔI (3)
ΔV = current battery voltage−1battery voltage before measurement cycle ΔI = current current−1current before measurement cycle

In addition, when using formula (3), the resistance is not always required, and the current change ΔI is required to be large to some extent (for example, a change of 0.1 C or more). Therefore, when the current change ΔI is small and the value of the DC resistance R cannot always be prepared, the resistance value obtained when the previous current change occurs is avoided by using it. In addition, as a method using a table, a method described in “JP 2000-258513 A” may be used.

Further, the polarization voltage Vf may be obtained based on the past voltage and current by using the method described in “Japanese Unexamined Patent Application Publication No. 2007-171045”.

(Description of step S24)
In step S24, the charging rate (SOC) is estimated from the open circuit voltage of the battery. Note that the process of step S24 corresponds to the process of the SOC estimation map 16 in the functional block diagram of FIG. The charging rate (SOC) in the present embodiment is defined by Equation (4), but as an actual estimation method, a charging rate-open voltage map prepared in advance is used.
SOC = 100 × current charge amount [Ah] / initial full charge capacity [Ah] (4)

FIG. 7 shows an example of an open-circuit voltage-charge rate (SOC) map. The map shown in FIG. 7 shows a case where the relationship between the open circuit voltage and the SOC does not change depending on the battery temperature, and is composed of a data group in which 0% to 100% of the SOC is divided in 10% increments. FIG. 8 is a graph showing the map of FIG.

As an example, a description will be given of how to obtain an SOC using a map when the open circuit voltage estimated in step S23 is 3.71V. In the graph of the open circuit voltage-SOC shown in FIG. 8, SOC = 54% is obtained as the SOC corresponding to the open circuit voltage 3.71V. However, when the SOC is actually estimated from the map of FIG. 7, it is estimated by the method described below.

First, the data closest to 3.71 V is searched from the open voltage data group in the column shown on the left side of FIG. Here, it becomes 3.8V in the seventh stage. Next, since 3.71V has a smaller value than 3.8V, the sixth-stage data which is voltage data one rank lower than 3.8V is selected. A value may be obtained by linear interpolation from these two points (data). In that case, since the SOC at 3.65V is 50% and the SOC at 3.8V is 60%, the SOC is 50+ (60−50) × (3.71−3.65) = 54. [%]It is estimated to be. Although linear interpolation is used here, data estimation by well-known spline interpolation may be used using four points including 3.55 V data and 3.9 V data. As a method of spline interpolation, for example, the method described in “Yoshimoto Safuji-shi: Spline function and its application (mathematics of new application series 20), Education Publishing 教育 (1979/01)” is used.

Here, how to obtain the voltage per 1% of SOC in the above-described equation (1) will be described. FIG. 8 shows the characteristics of the ideal battery 31. Here, the width of SOC1% when SOC is 80% is 79.5% to 80.5%. The difference between the open circuit voltage at 80.5% and the open circuit voltage at 79.5% is ΔV. This open-circuit voltage difference ΔV is defined as a voltage per 1% SOC. Here, an example in which the SOC is 80% is shown, but the same calculation is performed for other SOCs (for example, 40%).

(Description of step S25)
In step S25, a data pair (charge, SOC) stored in the SOC / charge storage unit 14 is added. The process of step S25 corresponds to the process of the SOC / charge storage unit 14 in the functional block diagram of FIG. As a method of adding a data pair, it may be recorded every time a data pair is acquired, but may be recorded when there is a change of 1% or more from the previously recorded SOC without recording each time. .

When a large amount of data cannot be stored due to the memory capacity or when old data is deleted to prevent error deterioration, the data stored in the SOC / charge storage unit 14 is appropriately deleted. Also good. As a reference for data deletion, for example, data that has been accumulated for a certain period of time after accumulation is used. The fixed time T is determined by the charge error caused by the ammeter error.

Specifically, the error of the ammeter 10 is divided into an offset error and white noise, and the respective values are defined as Io [A] and Iw [A] (see the catalog value of the ammeter, or Determined by actual measurement). Then, if the error of the full charge capacity given in advance is Qe [Ah], T [h] satisfying the following equation (5) is set as the above-mentioned fixed time T. The error Qe is determined as Qmax × ε using the error rate ε of the full charge capacity Qmax. The value of the error rate ε may be 5%, for example. ΔT is the current integration time step [h].
Io × T + Iw × √T × ΔT = Qe (5)

FIG. 9 is a diagram showing a table in the SOC / charge storage unit 14, and an example of processing of the SOC / charge storage unit 14 will be described with reference to FIG. A data pair consisting of SOC and electric charge is stored together with the measurement time. The charge is an integral value from the initial value, the unit is Ah, and the discharge side is positive. In the example shown in FIG. 9, the data at the measurement time 10:10 is the initial value, the initial value of the SOC is 60%, and the initial value of the charge is 0%. When there is a 1% SOC change from the previous SOC, the SOC and charge at that time are stored.

2) From the 2nd stage to the 4th stage, since the SOC is decreased by 1%, it is a data pair obtained at the time of discharging. Since the charge is positive on the discharge side, the charge is increasing. On the other hand, when moving from the fourth stage to the fifth stage, the SOC increases and the charge decreases. That is, charging is performed between the fourth stage and the fifth stage. The lowermost data pair indicates the latest data, and the SOC is 46% and the charge is 1.41 Ah.

The example shown in FIG. 9 shows a case where the relationship between the SOC and the open circuit voltage does not change depending on the temperature. However, when a battery whose relationship between the SOC and the open-circuit voltage varies depending on the temperature is a target, a table as shown in FIG. 9 is prepared for each temperature, and the table is selected according to the value of a thermometer separately attached to the battery. . The data at the measurement time is used when deleting the above-mentioned old data to prevent error deterioration or to prevent the memory from overflowing.

(Description of step S26)
In step S26, it is determined whether to update the full charge capacity. If the update condition is satisfied, the process proceeds to step S27. If the update condition is not satisfied, the process proceeds to step S28. Note that the process of step S26 corresponds to the process of the update command unit 17 in the functional block diagram of FIG.

As an update condition in step S26, the difference between the SOC minimum value and the maximum value in the data group stored in the table of FIG. 9 is taken, and the battery is fully charged when the difference is equal to or greater than a predetermined value. Update the capacity. Even if it is updated once, if this update condition is satisfied, the update is performed after the next data addition. As this predetermined value, for example, a fixed value such as 20% or 15% is used.

(Description of step S27)
In step S27, the full charge capacity of the battery is estimated based on the pair data of SOC and charge. In addition, the process of step S27 corresponds to the full charge capacity calculation part 18 in the functional block diagram of FIG. For the estimation of the full charge capacity, the relationship of the following equation (6) is used, where SOC is x, charge is y, and the slope of a straight line indicating the relationship between x and y is obtained as the full charge capacity. The target data pair is all data stored in the SOC / charge storage unit 14.
Charge = full charge capacity x SOC + constant (6)

When specifically obtaining the full charge capacity, for example, the least square method is used. As a method of least squares, the method described in the reference “The University of Tokyo Faculty of Liberal Arts, Statistics Department: Introduction to Statistics, University of Tokyo Press, September 25, 2001, 20th edition” may be used. Here, the reason for using the inclination is that, for example, when the SOC estimation shift occurs, the approximate straight line may move up and down on the coordinates, but the inclination is not affected, so that it is resistant to bias error deviation in the SOC estimation. It is.

The method for obtaining the full charge capacity will be described with reference to FIG. FIG. 10 is a plot of the data of FIG. 9 on coordinates where the horizontal axis is charge [Ah] and the horizontal axis is SOC [%]. The data in the fifth row in FIG. 9 is the point D1 in FIG. 10, and for the plotted data group, the approximate straight line obtained by the least square is L1. The slope of this straight line L1 represents the full charge capacity. In the example shown in FIG. 10, the slope is 0.1 Ah / SOC%, and the full charge capacity is calculated as 10 Ah, which is 100 times. SOH (degree of deterioration) is calculated as a 100% ratio of [full charge capacity] / [full charge capacity of a new battery].

(Description of step S28)
In step S28, display update processing of the display unit 19 is performed. FIG. 11 shows a display example of the display screen of the display unit 19. In the example shown in FIG. 11, the SOC, SOH, and remaining operation time are displayed. In FIG. 11, 81 indicates SOC, 82 indicates full charge capacity, 83 indicates SOH, and 84 indicates remaining usage time.

As for SOC, not only the percentage display by numerical value but also the SOC display with the bar display 86 of the battery display 85 for easy visual understanding. Therefore, the amount that can be used is indicated by the size of the portion denoted by reference numeral 86. Similarly, SOH is displayed on the bar display 87 of the battery display 88 as well as the percentage display by numerical values.

The display on the display unit 19 is updated every time the charging rate is calculated. However, when the process proceeds from step S22 to step S28, the full charge capacity has not been calculated, so the SOH at the current processing timing is not calculated. The value of the full charge capacity has not yet been determined. In that case, the display color may be changed to display the final value when the previous operation was performed. Alternatively, instead of changing the display color, a blinking display may be used. The user can recognize from the display color that the SOH and the full charge capacity are not the latest.

As the SOC, “100 × (current charge−charge of latest data stored in the SOC charge storage unit) / (full charge capacity)” is added to the latest SOC value measured by the SOC estimation map 16 of FIG. It may be an added value. The remaining usage time may be calculated by the following equation (7). The average current may be the average value of currents for the last 30 minutes (or 30 minutes instead of 30 minutes).
Remaining usage time = (current SOC-minimum SOC) x full charge capacity / average current x 100
... (7)

In the above-described embodiment, the case where there is one battery has been described as an example, but the present invention can be similarly applied to a case where a plurality of batteries are connected in series and parallel. Hereinafter, a case where a plurality of batteries are connected in series and parallel will be described using the example shown in FIG.

FIG. 12 shows an example in which a total of four 2 series batteries are connected in parallel. That is, the

batteries

911A and 911B connected in series and the batteries 912A and 912B connected in series are connected in parallel.

Ammeters

901 and 902 are provided at the places connected in series. For each of the

batteries

911A, 911B, 912A, and 912B,

measurement units

903, 904, 905, and 906 that can periodically measure current and voltage simultaneously are provided.

In addition, the measurement start of the AD (Analog-to-Digital) circuit of a current sensor and a voltage sensor is performed synchronously between the measurement unit 903 and the measurement unit 904 provided in the batteries 912A and 912B connected in series. Similarly, between the measurement unit 905 and the measurement unit 906 provided in the

batteries

911A and 911B connected in series, the measurement start of the AD circuit of the current sensor and the voltage sensor is performed in synchronization. Therefore, a synchronization signal is input from the synchronization unit 920 to each

measurement unit

903, 904, 905, 906. Furthermore, calculation units 907 to 910 that perform the processing shown in FIG. 2 are provided for the measurement units 903 to 906, respectively. The display unit 913 performs display as shown in FIG. 13 based on the calculation results of the calculation units 907 to 910.

Next, a method for calculating the remaining usage time in the entire battery group will be described. The full charge capacity and SOC for each of the

batteries

911A, 911B, 912A, and 912B are calculated by calculation units 907 to 910 shown in FIG. The capacity and remaining operation time of the entire battery are calculated by the following equations (8) and (9). The average current is, for example, the average value of currents for the last 30 minutes (or 30 minutes instead of 30 minutes).
Capacity [Ah] = {Battery 911A full charge capacity x Battery 911A charge rate + Battery 911B full charge capacity x Battery 911B charge rate + Battery 912A full charge capacity x Battery 912A charge rate + Battery 912B full charge capacity x Battery 912B charge rate} / 100 (8)
Remaining operation time = capacity / average current (9)

FIG. 13 is a diagram showing a display example. The display unit 913 includes a deterioration state screen 101 that collectively displays the deterioration state of each battery, a charge rate display screen 102 that collectively displays the charge rate state of each battery, and a battery group. The remaining usage time display 103 displays the total remaining usage time, and a display screen 104 displays which battery is deteriorated.

Degradation state screen 101 shows the SOH of

batteries

911A, 911B, 912A, and 912B connected in two series and two in parallel (degree of degradation: 100% ratio of [full charge capacity] / [full charge capacity of new battery] here) Display each. In FIG. 13, the SOH display corresponding to the battery 911 </ b> A of FIG. 12 is the display 105 </ b> A, and the SOH is displayed by the bar display 107 and the numerical display “SOH 70%” is displayed in an overlapping manner. The

displays

105B, 106A, and 106B are SOH displays corresponding to the

batteries

911B, 912A, and 912B, respectively.

The charging rate display screen 102 has the same configuration as the deterioration state screen 101, and the

displays

108A, 108B, 109A, and 109B are charging rate displays corresponding to the

batteries

911B, 912A, and 912B, respectively. The charging rate is indicated by the bar display 110 and the numerical value display “SOC 70%” is displayed in an overlapping manner.

The display screen 104 displaying the deteriorated battery displays a battery number whose SOH value is equal to or less than a predetermined threshold value. As this threshold value, for example, a fixed value of 50% may be used. If there is a battery for which the value of the full charge capacity has not been determined, the SOH value of the corresponding battery on the deterioration state screen 101 in FIG. The value of the usage time display 103 is tentatively calculated using the full charge capacity at the previous operation and is displayed in gray. After the value is confirmed, the value is displayed in black.

As described above, in the present embodiment, the battery current value and the terminal voltage value at the time of charging and discharging the battery are measured, and the charging rate and the deterioration degree as the battery state are measured based on the measured current value and the terminal voltage value. And a battery state estimation method for calculating at least one of a full charge capacity, and when a change in measured current value per second is equal to or greater than a predetermined value, a predetermined time has elapsed since the occurrence of the current change. The current value and terminal voltage value measured during the period until the battery is not used, and the battery charge rate, deterioration degree, and fullness are measured based on the current value and terminal voltage value measured during the battery charge / discharge period other than the above period. At least one of the charge capacities was calculated.

As described above, since the battery state is calculated using the current value and the terminal voltage detected during charging / discharging, even when there is no clear battery suspension state in the power system or electric vehicle, The battery state can be estimated.

Furthermore, since the current value and the terminal voltage value immediately after a current change of a predetermined value or more are transient values, calculating the battery state using them results in a value with a large error and lacking reliability. However, in the present embodiment, when measuring the current value and the terminal voltage value during charging / discharging, if the current change per second is greater than or equal to a predetermined value, a transient period until a predetermined time elapses. Since the detected current value and terminal voltage value are not used, the battery state can be calculated with higher accuracy. Note that the same processing as when there is a change in current of a predetermined value or more may be performed at the beginning of current flow at the start of operation.

As a configuration of the battery management system, an ammeter 10 that detects the current value of the battery B, a voltage detection unit 12 that detects a terminal voltage value of the battery B, and a current value detected by the ammeter 10 per second. A measurement timing designating unit 15 that detects a current change whose change is equal to or greater than a predetermined value, and a current value and a terminal voltage value detected during a period from when the current change is detected by the measurement timing designating unit 15 until a predetermined time elapses. A battery state calculation unit that calculates at least one of a charging rate, a degree of deterioration, and a full charge capacity as a battery state based on a current value and a terminal voltage value that are not used and are detected in a battery charge / discharge period other than that period (For example, a full charge capacity calculation unit 18 for calculating a full charge capacity).

In addition, when a plurality of batteries are provided as shown in FIG. 12, measuring

units

903 and 904 that can periodically measure current and voltage for each

battery

911A, 911B, 912A, and 912B at the same time. , 905, 906 are provided. And a battery state should just be calculated about each of a some battery. As a result, the battery state of each battery can be calculated with high accuracy.

Furthermore, by providing the

display units

19 and 913 which are display devices that display the battery state calculated by the battery state calculation unit, the user can easily recognize the battery state. When displaying the full charge capacity, if the full charge capacity corresponding to the charging rate is not calculated, the most recently calculated full charge capacity and the degree of deterioration of the battery based on the full charge capacity are displayed. . By doing so, the full charge capacity and the degree of deterioration are always displayed in the same manner as the charge rate, and the user can know the outline of the battery state even when the full charge capacity is not calculated.

When displaying the most recently calculated full charge capacity and the degree of deterioration of the battery based on the full charge capacity, the full charge capacity corresponding to the charge rate is displayed as a display form of the full charge capacity and the degree of deterioration. By making it different from the display form in the case, it can be easily understood that the full charge capacity and the deterioration degree are not the current values but the latest values.

Furthermore, by displaying the battery status for each of a plurality of batteries, it is easy to determine which battery has deteriorated, and maintenance such as battery replacement can be performed at an appropriate timing.

In the above-described embodiment, the battery B represents a management unit. For example, each of a plurality of battery cells included in the battery module 9 of FIG. 14 may be the battery B, and each cell group may be the battery B. Alternatively, each of the battery blocks 9A and 9B may be a battery B, and of course, the battery module 9 may be a battery B. In the example shown in FIG. 14, all the battery cells are connected in series, but a configuration including series connection and parallel connection may be used. Further, when the display as shown in FIG. 13 is performed, all the battery cells included in the battery module 9 may be displayed, but for each battery replacement unit, for example, for each of the battery blocks 9A and 9B in FIG. It is realistic and preferable to display the average value.

Although various embodiments and modifications have been described above, each embodiment may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Claims

Measure the battery current value and terminal voltage value when charging and discharging the battery, and calculate at least one of the charging rate, deterioration degree, and full charge capacity as the battery state based on the measured current value and terminal voltage value A battery state estimation method comprising:
When the change per second of the measured current value is greater than or equal to a predetermined value, the current and terminal voltage measured during the period until the predetermined time elapses from the occurrence of the current change is not used, A battery state estimation method for calculating at least one of a charging rate, a deterioration degree, and a full charge capacity of the battery based on a current value value and a terminal voltage value measured in a battery charging / discharging period other than the period.
A current detector for detecting the current value of the battery;
A voltage detector for detecting the terminal voltage value of the battery;
A current change detection unit for detecting a current change in which a change per second in a current value detected by the current detection unit is equal to or greater than a predetermined value;
The current value and the terminal voltage value detected during a period from when the current change is detected by the current change detection unit until a predetermined time elapses are used, and the current value detected during the battery charge / discharge period other than the period and A battery management system comprising: a battery state calculation unit that calculates at least one of a charge rate, a deterioration degree, and a full charge capacity as a battery state based on a terminal voltage value.
The battery management system according to claim 2,
A battery management system that uses the smallest polarization time constant of the battery polarization time constant or 2 seconds for the predetermined time.
The battery management system according to claim 2 or 3,
A battery management system using a current value corresponding to 0.1 C in terms of discharge rate as a change in current value per second.
In the battery management system according to any one of claims 2 to 4,
A battery management system comprising a display device that displays the battery state calculated by the battery state calculation unit.
In the battery management system according to any one of claims 2 to 4,
Of the charging rate calculated by the battery state calculation unit, comprising a storage unit for storing a charging rate within a predetermined number retroactive from the present time,
The battery management system in which the calculation of the full charge capacity by the battery state calculation unit is performed when the difference between the maximum value and the minimum value of the charge rate stored in the storage unit is greater than or equal to a predetermined charge rate difference.
The battery management system according to claim 6, wherein
A battery management system in which the predetermined charging rate difference is 15%.
The battery management system according to claim 6 or 7,
A display device that displays the battery state calculated by the battery state calculation unit;
The display device
When the charging rate is calculated by the battery state calculation unit, the display of the charging rate is updated with the calculated charging rate,
A battery management system that displays the most recently calculated full charge capacity and the degree of battery deterioration based on the full charge capacity when the full charge capacity corresponding to the charge rate is not calculated.
The battery management system according to claim 8, wherein
When displaying the most recently calculated full charge capacity and the degree of deterioration of the battery based on the full charge capacity, the full charge capacity and the degree of deterioration are displayed as the full charge capacity corresponding to the charge rate. Battery management system different from the display form of the case.
The battery management system according to claim 2,
The battery is composed of a plurality of battery cells,
The battery state detection unit is a battery management system that calculates at least one of a battery charge rate, a deterioration degree, and a full charge capacity for each of the plurality of battery cells.
The battery management system according to claim 2,
The battery includes a plurality of battery blocks including a plurality of battery cells,
The battery state detection unit is a battery management system that calculates at least one of a battery charge rate, a degree of deterioration, and a full charge capacity for each of the plurality of battery blocks.
The battery management system according to claim 10 or 11,
The connection of the plurality of batteries includes at least a series connection,
Synchronizing the detection by the current detection unit and the detection of each battery by the voltage detection unit so that the detection of the current value and the terminal voltage value are performed simultaneously between the plurality of batteries connected in series. Battery management system with device.
The battery management system according to claim 11,
A display device that displays the battery state calculated by the battery state calculation unit;
The display device is a battery management system that displays the battery state calculated by the battery state calculation unit for each of the plurality of battery blocks.